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High-Resolution Sequence and Event Stratigraphy of the Trenton-Utica Succession in Ohio: New Insights into the Late Ordovician Paleogeography of Eastern Laurentia

Mclaughlin, Patrick I., Carlton E. Brett, and Sean R. Cornell
H. N. Fisk Laboratory for Sedimentary Geology, Department of Geology, University of Cincinnati, Cincinnati, OH

The Upper Ordovician (Mohawkian-Cincinnatian) Trenton-Utica succession in Ohio comprises ~200 meters of limestone and shale in complex facies relationships. The Trenton-Utica succession of Ohio was studied in great detail from 20 drillcores and numerous outcrops along the Ohio River Valley to ascertain their relations to age equivalent strata in Kentucky and to establish a high-resolution sequence stratigraphic interpretation for this interval. Previous attempts to recognize individual lithologic units, characterized in outcrops of Kentucky, have only been partially successful. The use of sequence and event stratigraphy, which combine analysis of vertical and lateral facies changes with correlation of unique marker beds, enables identification of all the members of the Lexington Limestone of Kentucky in Ohio.

Comparison of the vertical facies succession of the Trenton-Utica interval in Ohio with age equivalent strata across eastern North America reveals very similar patterns, suggesting an extremely widespread process (i.e. eustacy) as the primary mechanism controlling facies distribution through time. Lateral facies successions vary slightly between depositional sequences reflecting adjustments of the basement through time in response to tectonic loading of the cratonic margin during the second tectophase of the Taconic orogeny. Furthermore, the sequence-based analysis suggests a need for revision of paleogeographic reconstructions of the mid-continent area, including reevaluation of the enigmatic Sebree Trough. Comparisons of lateral facies distributions between sequences suggest that certain local basins and arches evolved rapidly. Such episodes of topographic restructuring in many cases correspond to widespread intervals of soft-sediment deformation and K-bentonite horizons, suggesting increased seismicity.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004